Can Interior Primer Be Used On The Exterior?
October 1, 2015 12:15 PM   Subscribe

I have a very small, outdoor paint job to do. I am out of exterior primer, but have lots of interior primer. Can I use interior primer for under exterior painting?

I'm doing a small paint job to do on the outside of the house, stripping and repainting a milkbox (a small wooden panel with a door set into a brick wall). I have the latex paint. I had exterior latex primer, but someone borrowed it, and I won't get it back in time for this weekend when I'll be painting. I am reluctant to buy more exterior primer, since it really is a small job and we're at the end of the painting season anyway. I have tons of interior primer. Can I use interior latex primer for under exterior latex paint? Is this something I can get away with?
posted by Capt. Renault to Home & Garden (6 answers total)
For exterior wood, the best type of paint to use is oil.
posted by fimbulvetr at 12:39 PM on October 1, 2015

Sure. Someone will probably tell you it's a terrible idea, but I would be inclined to just try it and then repaint next year if it doesn't hold up well. Particularly if it's a small job.

Alternatively, you could try priming with the exterior topcoat paint... some are advertised as self-priming, meaning you can do both coats (although I still use a primer with those anyway).

It would be different if you were painting your whole house or something.
posted by selfnoise at 12:42 PM on October 1, 2015 [4 favorites]

I'd put two coats of the primer on, just to make sure.
posted by Thorzdad at 12:43 PM on October 1, 2015

Best answer: It will work, but last for about two weeks, tops. Maybe a bit longer if it is outside but tucked away out of any elements.

Oil used to be the best solution, but there are amazing latex options now, even water-based, albeit they still need to be exterior versions.

More than one coat of primer defeats the purpose and is often worse than no primer at all. The first coat will seal, the second coat will slide around, causing the finish coat to slide off, too.

I sold paint for a decade...
posted by TinWhistle at 1:35 PM on October 1, 2015 [2 favorites]

I work in residential construction. I'm not a painter but I work with them and am sometimes called on to do the odd bit of painting here and there. I've never heard of anyone reputable using an interior primer or paint for an exterior job, even for a very small job or just to finish off the bottom of a can.

If you could get away with it then people would definitely do it as it would save time and money, which are two things that contractors constantly worry about. Since people aren't doing it, I feel confident in saying that it's because it would fail in a really noticeable way. (Tradespeople frequently cut corners where they feel it won't matter or be noticed; a lot of being a successful tradesperson is knowing what you can and can't get away with.)

Oil paint, at least where I am, is rarely used anymore except in specialty applications. Good-quality latex paint is more than good enough for almost everything these days, and is much easier to work with. Go to the hardware store or paint store, get yourself a gallon of exterior latex primer, and save yourself the headache of dealing with a failed paint job.
posted by Anticipation Of A New Lover's Arrival, The at 2:38 PM on October 1, 2015 [1 favorite]

Response by poster: Thanks, everybody. In the end, I found another leftover can with just enough left at the bottom. It's pretty sludgy, but I can make it work.
posted by Capt. Renault at 6:16 AM on October 2, 2015

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